Exposure to extreme heat and pollution may double risk of a deadly heart attack, study shows

(CNN) — As heat waves and wildfire smoke continue to affect parts of the United States, doctors are warning that people need to watch their heart health — particularly if they live in areas with high pollution levels.

The risk of a deadly heart attack may double when people are exposed to extreme heat and high levels of particle pollution, a new study found. The study, published Monday in the journal Circulation, found that extreme cold could also put patients at greater risk for a fatal heart attack.

The study looked at more than 202,000 heart attack deaths between 2015 and 2020 in Jiangsu province, China. It found that when temperatures were extremely high or low, or there was a high level of particulate matter pollution, there was a “significantly associated” risk that a person would die from a heart attack.

When there was extreme heat combined with high pollution levels, people faced the greatest risk that they would die from a heart attack.

Older people and women seemed to be most at risk.

Particulate matter, or particle pollution, is the mix of solid and liquid droplets floating in the air, according to the Environmental Protection Agency. It can come in the form of dirt, dust, soot or smoke. Particulate pollution comes from coal- and natural gas-fired plants. Cars, agriculture, unpaved roads, construction sites and wildfires can also create it.

This study focused on the harm caused by the tiniest particulate matter: PM2.5. It’s so tiny — 1/20th of a width of a human hair — that people can’t see it, and it can travel past the body’s usual defenses.

Instead of being breathed out, it can get stuck in the lungs or go into the bloodstream. The particles cause irritation and inflammation and can lead to respiratory problems. Long-term exposure can cause cancer, stroke and heart attack.

On days when the pollution was above 37.5 micrograms per cubic meter and a heat wave lasted four days, the risk someone would die from a heart attack was twice as high than usual. Cold snaps and high pollution days didn’t seem to have the same increase.

Extreme temperatures did not mean that the thermometer had to hit 100 degrees Fahrenheit. Rather, extreme high temperatures were considered a range between 82.6 to 97.9 degrees Fahrenheit. At that temperature, during a two-day heat wave, the risk of dying from a heart attack was 18% higher. It was 74% higher during a four-day heat wave when the temperatures ranged from 94.8 to 109.4 degrees Fahrenheit.

During cold days, when the temperatures ranged from 33.3 to 40.5 degrees Fahrenheit for two days, the risk was 4% higher.

Ultimately, researchers estimate up to 2.8% of heart attack deaths may be attributed to the combination of extreme temperatures and high levels of fine particulate matter pollution.

“Extreme temperature events are becoming more frequent, longer and more intense, and their adverse health effects have drawn growing concern,” said senior author Yuewei Liu, an association professor of epidemiology in the School of Public Health at Sun Yat-sen University in Guangzhou, China.

As there are more extremes of high temperatures and cold snaps due to the climate crisis, the authors argue that people will need to pay much closer attention to the weather before they go out and take the proper precautions if they want to take care of their heart health.

People who are vulnerable to having a heart attack in extreme temperatures — those with underlying health conditions, the elderly and the young, and in some cases women — should be sure to stay indoors on hot, high pollution days, the authors said.

Use an air purifier in the house to cut down on pollution exposure. Use fans and air conditioners in hot weather, and if you have to go outside, try to go out early in the day when the temperatures are lower, and wear loose-fighting lighter colored clothing.

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